Classification and identification of rock blastability in open-pit mine based on comprehensive weighted cloud model

Blasting operation in open-pit mine requires uniform fragmentation, low proportion of large fragments, and high efficiency of shoveling and transportation equipment. Blasting evaluation of rock mass is an important basis for blasting parameters optimization, quality improvement and cost reduction. In order to carry on the scientific classification to the rock mass blastability, five indexes, such as rock firmness coefficient, tensile strength, rock density, longitudinal wave velocity of rock and longitudinal wave velocity of rock mass, were selected to establish the blastability classification index system, the classification standard of rock mass blastability was determined, the cloud digital characteristics of rock mass blastability classification index were calculated, the cloud model of each index belonging to each rock mass blastability grade was generated, and a classification method of rock mass blastability based on comprehensive weight cloud model was proposed. The model has been applied in Pingshuo east open pit coal mine, the blastability grades of mudstone, sandy mudstone, siltstone, fine-grained sandstone, medium-grained sandstone, coarse-grained sandstone and marl in east open pit coal mine were determined. The rock mass blastability grade of mudstone, sandy mudstone, siltstone is Grade A, the certainty degrees are 0.585 5, 0.584 4 and 0.349 7, respectively.The grade of fine-grained sandstone is Grade C, the certainty degree is 0.149 4.The grade of medium-grained sandstone, coarse-grained sandstone and marl is Grade B, the certainty degrees are 0.253 2, 0.212 9 and 0.328 8, respectively.The certainty degree can accurately reflect the membership degree between each rock mass and each blastability grade, which is conducive to more accurate calculation of explosive consumption, and the conclusion has higher credibility and practicability.